Silk, artificial fibroin

The overall performance difference between the artificial fibroin silk and natural silk is induced by many factors. Composition of the spinning dope is critical but not the only factor. Important to understand is that the spinning process which determines the condensed structure of silk is crucial. It suggest that knowing the spinning process details it should be feasible to produce high-performance silk artificially and "design" silk. 

Pioneering work in fibroin wet spinning can be traced back to 1930s. After that, little work has been done until the late 1980s, when more research was done to investigate the spinning dope systems, and structure and properties of the artificial fibroin silk. The composition of the dope is very important to the properties of the final fiber. Several kinds of solvents, such as LiBr—EtOH, Ca(NOo,)2—MeOH, formic acid, HFIP, hexafluoro acetone (HFA), and so on, are used to prepare the spinning dope (Table 4). Very recently, an ionic liquid was used as dope solvent (Phillips et al., 2005). 

From a scientific perspective, the artificial silk experiments have provided insight into the morphology of reconstituted silk. In the spinning dope, fibroin molecules adapt a random coil or other less extended conformations. 

Yao, J.M., Masuda, H., Zhao, C.H., and Asakura, T. "Artificial spinning and characterization of silk fiber from Bombyx mori silk fibroin in hexafluoroacetone hydrate". Macromolecules 35(1), 6-9 (2002). 

Commercial and Artificial Processing. CommerciaUy, silkworm cocoons are extracted in hot soapy water to remove the sticky sericin protein. The remaining fibroin or stmctural silk is reeled onto spools, yielding approximately 300—1200 m of usable thread per cocoon. These threads can be dyed or modified for textile appHcations. Production levels of silk textiles in 1992 were 67,000 metric tons worldwide. The highest levels were in China, at 30,000 t, foUowed byJapan, at 17,000 t, and other Asian and Oceanian countries, at 14,000 t (24). Less than 3000 metric tons are produced annuaUy in each of eastern Europe, western Europe, and Latin America almost no production exists in North America, the Middle East, or Africa. 1993 projections were for a continued worldwide increase in silk textile production to 75,000 metric tons by 1997 and 90,000 metric tons by 2002 (24). 

Zhou, G., Shao, Z., Knight, D.P., Yan, J., and Chen, X. Silk (2009) Fibers extraded artificially from aqueous solutions of regenerated Bombyx Mori silk fibroin are tougher than their natural counterparts. Advanced Materials, 21, 366-370. 

Zhao, C., Yao, J., Masuda, H., Kishore, R., Asakura, T., 2003. Structural characterization and artificial fiber formation of Bombyx mori silk fibroin in hexafluoro-iso-propanol solvent system. Biopolymers 69 (2), 253—259. 

Commercial and Artificial Processing. Commercially, silkworm cocoons are extracted in hot soapy water to remove the sticky sericin protein. The remaining fibroin or structural silk is reeled onto spools, yielding approximately 300-1200 m of usable thread per cocoon. These threads can be dyed or modified... 

Significant improvement of functional properties has been reported for fibers obtained from blends of chitin with various natural polymers such as cellulose, silk fibroin and glycosaminoglycans [48, 50, 51]. Fibers of chitosan blended with alginate, collagen and gelatin have been evaluated for wound dressing and artificial skin applications [52, 53, 108, 136]. 

PU is a strong, hard-wearing, tear-resistant, flexible, oil-resistant, and blood-compatible polymer. The functional properties of natural macromolecules can be merged with those of synthetic polymers having controllable structures and properties for the production of polymer/protein hybrids. In tissue engineering, silk fibroin/PU blend film can be used as scaffold material for artificial blood vessels [466] (Figure 2.62). Bacterial synthesized cellulose, which was designed... 

Kasoju, N., Bora, U. Silk fibroin based biomimetic artificial extracellular matrix for hepatic tissue engineering applications. Biomed. Mater. 7(4), 045004 (2012)... 

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